Conventionally, an air conditioner includes an outdoor unit including a compressor, a plurality of indoor units, each including an indoor expansion valve and an indoor heat exchanger, a liquid-refrigerant connection pipe and a gas-refrigerant connection pipe that connect the outdoor unit and the indoor units to each other, and at least one relay unit disposed in the liquid-refrigerant connection pipe and the gas-refrigerant connection pipe and configured to individually switch the plurality of indoor heat exchangers so that each of the plurality of indoor heat exchangers functions as a refrigerant evaporator or a refrigerant radiator. Such an air conditioner is described in PTL 1 (Japanese Patent No. 5517789), in which a liquid connection pipe (a refrigerant pipe connected to the liquid-refrigerant connection pipe) and a gas connection pipe (a refrigerant pipe connected to the gas-refrigerant connection pipe) in the relay unit are each provided with a relay shutoff valve (a liquid relay shutoff valve and a gas relay shutoff valve) such that when refrigerant leakage occurs, the liquid relay shutoff valve and the gas relay shutoff valve are closed to prevent the flow of refrigerant into an indoor unit from the outdoor unit to suppress leakage of refrigerant from the indoor unit.